Fresh
vegetables bought "out of season" may have much higher levels
of nitrates - linked by some to ill-health - than frozen alternatives.
Researchers say that fresh vegetables which have been imported
from a distant country may also have fewer nutrients.
UK
supermarkets offer seasonal vegetables such as broccoli all
year round.
However, a survey by the Austrian Consumers' Association suggests
that the extra price paid by shoppers may not always be worthwhile
in health terms.
The
longer food is stored, the more nutrients degrade
Spokesman, Food Standards Agency
It
said that some winter crops tested were higher in nitrates
- which can be converted into nitrites in the body.
Although there is no strong evidence linking these to ill-health,
some experts still believe that our consumption of nitrates
should be kept in check.
Vitamin fall
Conrad Brunnhofer, the researcher involved in the study, told
BBC News Online that nitrate levels were more than seven times
higher in some fresh vegetable samples compared with frozen.
He said: "There is more than one reason why I would prefer
frozen vegetables to fresh vegetables out of season.
"The problem of nitrates is one of these."
Previous research from the association has pointed to a reduction
in vitamins in vegetables imported during the winter months.
Frozen fast
Any vegetable will start to lose nutrients from the moment
it is harvested.
However, while the freezing process can take place within
hours of the vegetables being picked, it may be some time
before fresh vegetables reach supermarkets in the UK.
We import many of our vegetables from other parts of Europe,
or even other continents, meaning a long journey in a refrigerated
container.
The association found that vegetables such as broccoli lost
significant amounts of nutrients when imported "fresh", and
ended up less nutritious than their frozen equivalent.
The UK government is trying to encourage fruit and vegetable
consumption as a way of cutting rates of cancer, coronary
heart disease and stroke.
The current recommendation is five portions of fruit or vegetables
a day.
A spokesman for the Food Standards Agency told the BBC that
it did not matter for these purposes whether the portion was
fresh or frozen vegetables.
She said: "The longer food is stored, the more nutrients degrade.